I don't can you explain it please. I know arbitrage only from gambling and maybe dropshipping and guessing it is a similar theory but do not know the details for this sphere.
Many markets work with order books, see my graphic to get an impression how these order books look like.
Be aware that I just copied the order book of one market three times and labeled them as Market1, Market2, Market3.
In reality the order books of all three markets would have different prices and quantities in them.
Market1, Market2, Market3 could be different crypto exchanges, but the same principle is applicable for other assets and markets too.
An order book is filled with positions of traders, who are willing to buy/sell a specific amount for a specific price.
Where the sell order meet with the buy orders, lays normally the market price of that asset (sometimes it's taken the last traded price as market price).
If now in Market1 a bigger position is sold, it will clear out the buy order book side until the amount in total of the different executed orders in that order book
sums up to the amount of the sell position that was placed (see red arrow in graphic, sell of 26.19 ETH was done).
This can result in the situation that a buy position gets executed on Market1 for a much lower price (eg. 4'057.05) then it would be possible in Markets2 and 3
(as their order book stays untouched if nothing is bought/sold on those markets).
This allows somebody to buy cheap (eg. 4'057.05) in Market1, and then sell high priced in Market2 or 3 (eg. 4'273.78).
Keep in mind that not all price findings are made with order books, most of the eth tokens use pools
(that allows another possibility for arbitrage, I posted a thread about this few weeks ago).
That is a simple example of arbitrage trading. There are many others, please read this for a deeper understanding:
https://www.investopedia.com/terms/a/arbitrage.asp
Arbitrage trading equalizes different prices on different markets over time and help to provide a tight spread (gap between lowest sell order and highest buy order in the books).
